1. Field of the Invention
The present invention generally relates to computer apparatus and, in a preferred embodiment thereof, more particularly relates to keyboard structures for portable computers such as notebook computers.
2. Description of Related Art
In recent years the notebook computer has made considerable gains in both popularity and sophistication. One factor contributing to the increasing popularity of the notebook computer is its ever decreasing size and weight, a factor arising from the ability to fabricate various components of the computer in smaller and smaller sizes while, in many cases, increasing the power and/or operating speed of such components.
One continuing challenge in the design of notebook computers, however, is their keyboard structure. This design challenge arises from two conflicting design goals--the desire to even further reduce the size of the keyboard structure, and the desirability of having he notebook computer emulate as closely as possible the size and typing "feel" of a desktop computer keyboard.
There are, of course, two dimensional factors which may be varied to reduce the size of a notebook computer keyboard structure--its horizontal dimensions (i.e., its length and width), and its vertical or thickness dimension. The horizontal dimensions of the keyboard are governed by the number, size, and relative spacing of the manually depressible key cap portions of the keyboard, and various reductions in these three dimensional factors may be utilized to reduce the overall length and/or width of the keyboard. However, as will be readily appreciated, a reduction in these three configurational aspects to gain a keyboard size reduction correspondingly lessens he similarity of the notebook computer keyboard in appearance, key arrangement and typing feel to its desktop counterpart.
Similar restraints are also presented when attempts are made to reduce the overall thickness of a notebook computer keyboard. One possibility which has been investigated and attempted is to simply reduce the keystroke distance in the notebook computer keyboard compared to its desktop counterpart. Using this design technique, the overall thickness of the notebook computer in its closed storage and transport orientation may be correspondingly reduced. However, this thickness reduction in the overall notebook computer, achieved by reducing the keyboard keystroke distance, creates what many users consider to be an undesirable typing "feel" difference compared to the longer keystroke distance typically found in a larger desktop computer keyboard.
Another keyboard-directed approach to reducing the vertical thickness of a notebook computer in its closed storage and transport orientation is to provide a notebook computer keyboard with a collapsible construction in which, with the computer display screen lid opened, the keyboard keys are elevated to their normal operative positions, and with the display screen closed, the keys collapsed to reduce the thickness of the keyboard when the notebook computer is in its closed storage and transport orientation. Examples of collapsible notebook computer keyboards may be found in U.S. Pat. No. 5,532,904 to Sellers, and U.S. Pat. No. 5,602,715 to Lempicki et al, these patents being hereby incorporated by reference herein in their entirety.
In the collapsible notebook computer keyboards illustrated and described in these two patents, a dome sheet having a spaced series of elastomeric spring return domes underlies the keyboard's depressible key cap members which are supported on a monoblock structure, by scissor linkages, for vertical movement between extended and depressed positions. The dome sheet is shiftable relative to the keys between a first position in which the domes centrally underlie the keys and support them in elevated operating positions, and a second position in which the domes are horizontally shifted out of operative engagement with the keys and permit them to collapse toward the dome sheet to reduced height storage and transport orientations that correspondingly reduce the height of the keyboard.
A spring structure continuously exerts a horizontal biasing force on the dome sheet (either directly on the dome sheet or on the multi-layer circuit structure of which it is a part) which resiliently urges it toward its first position. When the notebook computer display screen lid is opened, the spring structure drives the dome sheet to its first position. Subsequently, when the display screen lid is closed, a structure on the lid engages an edge portion of the dome sheet (or the multi-layer circuit structure) and exerts a direct horizontal force thereon to shift it back to its second position.
While these two mechanisms for automatically collapsing a notebook computer keyboard in response to closing the computer's display screen lid portion advantageously reduce the overall keyboard thickness when the computer is in its closed storage and transport orientation, they also present several design difficulties. For example, it has proven to be somewhat difficult to meet the key collapse and elevation shifting motion tolerances required by the keyboard. Additionally, in these designs springs undesirably place several parts in stress over large areas thereof for extended time periods. Moreover, these designs undesirably require the computer to house mechanisms mechanically linking the lid housing to the shiftable portion of the keyboard.
In view of the foregoing it can be seen that a need exists for a collapsible notebook computer keyboard design which eliminates or at least substantially reduces the above identified design problems presented by previously proposed collapsible keyboard design. It is to this need which the present invention is directed.